Am I able to delete my submissions storage?

I noticed the notification that I am out of submission storage.  Am I able to delete older items in the storage?

If no action is taken, older submissions will be automatically deleted until you have only 500 submissions stored. But like this you cannot select which ones to keep, as they will be selected according to their date. 

If you wish to manually delete them you can select the form > submissions > Del or Delete all submissions:

Before deleting submissions you can first export your data:

https://www.jotform.com/help/374-How-to-export-all-of-your-data-at-once 

Let us know if we can assist you further.